Currently, demand for data communications has increased in mobile communication systems, and with increases in data communications, various techniques have been proposed to obtain high spectral efficiency.
One of techniques having the potential to enhance spectral efficiency is an OFDMA (Orthogonal Frequency Division Multiple Access) technique. In this technique, communications are performed using the same frequency in all cells in a communication area comprised of the cells, OFDM is used as a modulation scheme in communicating, and TDMA (Time Division Multiple Access) and FDMA (Frequency Division Multiple Access) is used as an access scheme. This technique provides a communication scheme where an isolation cell shares the common wireless interface with the cell area, and higher-speed data communications are achieved.
As scheduling of the OFDMA system, a method is proposed where in HSDPA (High Speed Downlink Multiple Access) in a W-CDMA (Wideband-Code Division Multiple ACcess) mobile communication system, a communication terminal apparatus reports CQIs (Channel Quality Indicator) that are information indicating downlink conditions of all subcarriers to a base station apparatus, and the base station apparatus performs scheduling of packets based on the CQIs of all the subcarriers reported from each communication terminal apparatus (Non-patent Document 1).
Similarly, the invention is published where in scheduling of transmission data in an OFDM system using a plurality of subcarriers, a communication terminal apparatus evaluates each of downlink channel conditions (frequency characteristics) and reports information obtained by quantizing each of the channel conditions to a base station apparatus using an uplink feedback channel, and the base station apparatus determines sub-carriers to assign to each communication terminal apparatus based on the reported information (Patent Document 1).    Patent Document 1: Japanese Laid-Open Patent Publication No. 2005-130491    Non-patent Document 1: “Comments on frequency scheduling and joint power and rate optimization for OFDM”, 3GPP, TSG RAN WG1 Meeting #29, R-02-1321, November 2002.